System and method for regulating access to direct access storage devices in data processing systems

摘要

A data processing system regulating access from a plurality of host computers to a plurality of direct access storage devices. The data processing system has a storage controller connected for data communication to the host computers by one or more channels per host computer. The storage controller is further connected to direct access storage devices used to provide auxiliary storage. The storage controller, responsive to host computer request, selectively establishes a communication link for data transfer between the host computers and the direct access storage devices. Channels are temporarily disqualified from obtaining control of the storage controller or a storage device during periods of contention for access to the storage devices or the storage controller. Transmission of device end and control unit end signals is also selective by channel. Override conditions are specified to allow for host computer or channel failure without disabling the data processing system.